Decompressive craniectomy (DC) is one of the therapeutic options for severe traumatic brain injury (TBI), and it has long been used for the treatment of patients with malignant post-traumatic brain edema. However, a lack of definitive evidence prevents physicians from drawing any conclusions about the efficacy of DC for the treatment of TBI. Magnetic resonance imaging (MRI) is widely used to evaluate the effects of TBI in both experimental and clinical studies. Therefore, the aim of the present study was to investigate the MRI assessment of DC post-TBI in rats to provide experimental animal data and radiological evidence to support the clinical application of DC. We used both in vivo MRI and proton magnetic resonance spectroscopy ((1)H-MRS) to evaluate the therapeutic effect of DC on lateral controlled cortical impact (CCI) rat models at 3h, 1 d, 2 d, 3d and 7d after TBI. Our data suggest that DC can reduce brain edema; decrease the apparent diffusion coefficient value, contusion volume and lactate (Lac)/creatine (Cr) ratio; and increase the N-acetylaspartate (NAA)/Cr and choline (Cho)/Cr ratios after TBI. The present results suggest that DC can indeed reduce brain edema formation and exhibits good neuroprotective efficacy after CCI injury in rats.